The Bose OE2i is one of the niftiest headphone designs I've ever seen, fitting into the supplied zippered case that's 5.0 x 5.25 x 1.5 inches thick when closed. This case can even fit into an ordinary man's jeans back pocket, although you would not want to sit on it. Bose warns about twisting the earcups past their design limit when rotating them, or applying any other pressures that could break the plastic parts. Unfolded and ready for use, they look like an ordinary on-ear headphone, and I never would have guessed they could fit into such a small carrycase. Besides being ultra-portable in the tiny carrycase, the OE2i can be worn around your neck all day long when not in use, by pulling the earcups all the way down so they don't bump against your chin.

The earpads are oval and flat - some kind of soft spongy material, perforated in the center where the sound comes out, and more or less identical to the earpads of the Bose QC3 or the B&W P5. The headphone weighs next to nothing, but the earpads put a mild pressure on the ears. I have headphones that weigh 10 times as much and exert 10 times the ear pressure, which doesn't bother me, but even the very mild pressure of the OE2i might bother people who aren't used to wearing headphones.

The headband is padded on the top and bottom, but for people who are bothered by even the slightest pressure on top of their head, I recommend pulling the earcups down a slight bit more than the minimum necessary for the fit, so the very light weight of the headphone is borne mostly by the earcups and not the headband. The headband has an internal metal construction, but how far the metal extends either way I can't tell since all I can see of the internal part is 1.5 inches on either side when the earcups are pulled all the way down.

The cable with a diameter of 2 mm is thin, but not quite as thin as the B&W P5's cable. The cable is single-sided and detachable, 4.5 ft.long, and terminated by a 45 degree angled miniplug. Apparently the OE2i differs from the OE2 only by the cable type - the OE2i having the Apple i-device controls. What is odd is the large price difference between the OE2 and OE2i, and that I don't see a replacement cable on the Bose site that has Apple controls. Perhaps there is a difference besides the cables? I don't know - the OE2i cable does detach, and the earcup end of the cable looks like a standard sub-miniplug, but what the point would be of detaching if the only replacement cable is the one without the controls, I don't know.

The OE2i is apparently intended to be a semi-open design, which leaks a small amount of sound when played loudly. This headphone might be OK for cubicle use when played at moderate volumes, but that's going to depend partly on the ambient noise level in the office, and partly on the sensitivity of the person(s) in the adjoining cubicles. The soundstage is about what I would expect of this type of design - not particularly wide or deep, but not especially constricted or closed-in either. The clarity and resolution seem typical to me for a small lightweight headphone - fine for portable use, but not as refined as the better headphones made for home/desktop use.

The default sound of the OE2i played flat with no EQ is rolled off somewhat on the high end compared to the more expensive headphones I have, so I applied "treble boost" EQ with the iPod Touch and iPhone4, and equivalent compensation when using Foobar2000 on the desktop computer. This EQ compensation made the overall response of the OE2i very similar to my better headphones, with just a few minor differences you would expect from a small lightweight headphone. Despite the treble boost, sibilants were less noticeable than with all but one of my more expensive headphones - the Shure SRH-1840 which sells for 4 times as much. I was not able to find specs such as impedance and sensitivity for the OE2i, but the efficiency is high enough to play average volume tracks loudly on iPods and iPhones.

Bass response is a very hot ticket with headphones these days, and many if not most of the headphones in the OE2i's price range are quite bassy. The Bose OE2i is not a bassy headphone in that sense - in fact its bass is lighter in strength compared to most of the better hi-fi headphones that don't have boosted bass. When real bass is present on the music track however, the impacts are very solid and gratifying. In spite of the very critical appraisal I made above, I find the sound quality of the OE2i good not only for portable use, but quite satisfactory for home use if a headphone made specifically for desktop hi-fi systems isn't handy.

A concern I had with the OE2i was the EQ I assumed that Bose applied to this headphone, possibly through passive electronic components in the earcups. Since I also applied treble boost EQ externally, I worried that the combination could introduce audible peaks and dips into the response, so I listened closely for any of those. So far nothing strikes me as significantly unbalanced. In the several headphone reviews I've done to date, I haven't suggested doing any burn-in as the initial listening with those (more expensive) headphones indicated a smooth sound that wouldn't change significantly after perhaps 50 to 100 hours of use. In the case of the Bose OE2i, I would suggest at least 30 to 50 hours of play time at good volume with dynamic music tracks before making a final judgement about the sound quality. Nothing specific - just a hunch.

Now that I've covered the basics of the sound, it's time to describe how the OE2i sounds with a variety of music that's available on CD's or as high-quality downloads from Internet music stores. I've used the following examples in other reviews, so these will serve as good test tracks for this review and the results can also be compared to the results noted in the other reviews.

Bauhaus - Bela Lugosi's Dead (~1980): Strong midrange sound effects - this is a good worst-case test for resonant-type sounds in the most sensitive midrange area. Handled very well by the OE2i.

Blues Project - Caress Me Baby (1966): Rarely mentioned, but one of the greatest white blues recordings ever. The loud piercing guitar sound at 0:41 into the track is a good test for distortion or other problems. Handled pretty well by the OE2i.

Boz Scaggs - Lowdown (1976): Good sound quality - this is a great test for any nasality in the midrange. Handled very well by the OE2i.

Buffalo Springfield - Kind Woman (~1968): A Richie Furay song entirely, rarely mentioned, but one of the best sounding rock ballads ever. This will sound good on most headphones, but it's very good with the OE2i.

Cat Stevens - Morning Has Broken (early 70's): A near-perfect test for overall sound - this track will separate the best sounding headphones from the lesser quality types. Nothing specific, except that almost any deviation from perfect reproduction will stand out with this track. Sounds good on the OE2i.

Catherine Wheel - Black Metallic (~1991): Goth with industrial overtones - I like this since it's a great music composition and the sound effects are smoothly integrated into the mix. This may sound distorted or mushy with some headphones, but the OE2i renders the deliberate instrumental distortions clearly.

Def Leppard - Bringin' On The Heartbreak (1981): MTV goth/pop/metal at its best - good ambience and high energy - the better headphones will separate the details and make for a good experience. Lesser quality and the details tend to mush together. Rendered well by the OE2i.

J.S. Bach - E. Power Biggs Plays Bach in the Thomaskirche (~1970): Recorded on a tracker organ in East Germany, the tracks on this recording have the authentic baroque sound that Bach composed for, albeit the bellows are operated by motor today. The OE2i plays the tones seamlessly through the upper limits of the organ, which are near the upper limits of my hearing.

Jamming With Edward - It Hurts Me Too (1969): Intended originally as a test to fill studio down time and set recording levels etc., this was released a few years later for hardcore Rolling Stones fans. Although not as good technically in every aspect as the Chess studio recordings of 1964, and in spite of the non-serious vocals by Mick Jagger, this rates very high on my list of white blues recordings, and sounds very good with the OE2i.

Jimmy Smith - Basin Street Blues (early 60's): This track has some loud crescendos of brass and other instruments that don't sound clean and musical on some headphones. The OE2i provides good reproduction - obviously superior to most lo-fi or cheap headphones, but not quite as detailed as the more expensive headphones I have. Listen particularly to the second crescendo at 15 seconds in, for maximum detail effect.

Ladytron - Destroy Everything You Touch (~2009): Featured in The September Issue, this song has heavy overdub and will sound a bit muddy on some headphones. Sounds very good with the OE2i.

Milt Jackson/Wes Montgomery - Delilah (Take 3) (1962): The vibraphone is heavily dependent on harmonics to sound right, and the OE2i plays it very well.

Pink Floyd/Dark Side of the Moon - Speak To Me (1973): Strong deep bass impacts will be heard and felt here.

Rolling Stones - Stray Cat Blues (1968): Dirty, gritty blues that very few white artists could match. On some headphones the vocals and guitar lack the edge and fall more-or-less flat. If you're a really good person, playing this song will probably make you feel nervous and uneasy.

Tony Bennett - I Left My Heart In San Francisco (1962): Frank Sinatra's favorite singer. Highest recommendation. With some of the best headphones, the sibilants on this recording are very strong, but they're no problem at all with the OE2i.